Conventionally, housings at drive shaft and idler shaft ends of a conveyor main frame of a relatively small belt conveyor designed for conveying mechanical component parts are typically mounted on the main frame in the fashion as illustrated in FIGS. 7(a) and 7(b).
Specifically, the conveyor main frame 1 consists of an elongated hollow rectangular box made of an extruded aluminum member, and a pair of housing blocks 2 each made of a planar plastic plate member are attached on either outer side wall 1c and 1d at each end portion of the conveyor main frame 1 by way of bolts 3 so as to form a housing 4 defined by the housing blocks 2 on either side.
As well known in the art, a pulley 5 is rotatably received between the inner surfaces 2a of the housing blocks 2 for each of the housings 4, one of which is a drive shaft end housing equipped with a motor not shown in the drawings while the other housing 4 is an idler shaft end housing.
An endless belt 6 is passed around the pulleys 5 of the drive shaft end and idler shaft end housings and along the upper and lower outer walls 1a and 1b of the conveyor main frame 1 so that the endless belt 6 may be moved under the driving force of the motor.
The assembling of the housings for such a conventional belt conveyor has substantially been carried out as described in the following with reference to FIG. 7(b).
First of all, one end of each of the housing blocks 2 consisting of a rectangular planar body is placed on a specified part of an outer wall 1c or 1d of an end portion of the conveyor main frame 1. Then, bolts 3 are passed through mounting holes 7 provided in the housing block 2, and then into slots 8 provided in the conveyor main frame 1 so as to thread the bolts 3 with nuts 9 provided inside the slots 8 and secure the housing block 2 to the conveyor main frame 1.
According to such a belt conveyor, it is necessary that the housing blocks 2 on either side of each end of the conveyor main frame 1 oppose each other with a high dimensional precision. Should there be any dimensional errors in the mounting positions of the housing blocks 2 on either side, the pulley 5 around which the endless belt 6 is passed may not be placed exactly perpendicularly to the feeding direction of the endless belt 6, and the endless belt 6 may sway laterally back and forth in its driven condition thereby rendering satisfactory and smooth operation of the belt conveyor impossible.
However, according to such conventional housing blocks 2, as they consisted simply of planar members which are simply attached to the planar outer side walls 1c and 1d of the conveyor main frame 1, it has been extremely difficult to accurately locate and secure housing blocks 2 so as to mount a pulley 5 perpendicularly to the feeding direction of the endless belt 6, and a considerable loss of efficiency has been unavoidable.
Further, since each end portion of the conveyor main frame 1 was provided with right angle corner edges, a considerable contact pressure was applied from the corner edges of the conveyor main frame 1 to the endless belt 6 as it moves from the upper or lower surface of the conveyor main frame 1 to one of the pulleys 5, or from one of the pulleys to the upper or lower surface of the main frame 1, and it presented a certain problem in regards to the long term durability of the endless belt 6.
Additionally, in many cases, guide bars and guide plates were attached to the outer side walls 1c and 1d of the conveyor main frame 1 to prevent mechanical component parts or the likes which are being conveyed from falling off from the belt conveyor, and the users had to prepare such attachments themselves. Since such attachments were normally fixedly secured to the conveyor main frame 1, and cannot be adjusted at will, there were cases in which it was not possible to entirely prevent mechanical component parts of different heights from falling off from the endless belt.